The present invention relates generally to lighting for photography, and more particularly, to a system for photographic exposure via real-time broadcast of lighting parameters.
Ambient or available lighting is often insufficient to allow a camera to capture and create a properly exposed image, including digital images. One well known effort to increase available light comprises flash devices. Flash devices are frequently built directly into the camera in consumer and hobbyist level cameras, while they are most often externally mounted to professional level digital single-lens reflex cameras, known as digital-SLRs or DSLRs.
Known flash devices, commonly referred to simply as “Flashes”, typically produce a flash of artificial light with a duration ranging from about 1/10,000 of a second to about 1/200 of a second, at a color temperature of about 5,500 Kelvin (K) to help illuminate a scene. While flashes are most commonly used to substantially increase the available light a scene, they are also used to capture objects moving quickly through the scene, or to change the quality of light of the scene.
To increase available light in a commercial setting, so-called “studio lighting” is used. Studio lighting typically comprises continuous lighting or strobe lighting, and frequently a combination of both continuous lighting or strobe lighting. A benefit of continuous lighting is that the photographer continuously receives feedback on how the subject looks in an image to be captured which allows the photographer to adjust either the angle and intensity of the lighting on the subject, or the settings on their camera, to achieve the desired exposure.
Lights used for continuous lighting are typically divided into two categories in the art known as “hot-lights” and “cool-lights”. Hot-lights typically comprise tungsten or halogen and become extremely hot to the touch during use, to the point of potentially burning a user. Since they become so thermally hot, hot-lights can cause a fire and may be uncomfortable if they're directed into a subject's eyes. A known issue with hot-lights is, that they may not generate sufficient light for photographing people. Resultantly, the studio photographer needs to set their camera to a relatively high ISO setting, which may detract from the quality of images being captured. They are also very “warm” in color temperature, typically around 7,500K, so it can be problematic to mix the color temperature emitted by hot-lights with daylight color temperature sources, such as a flash.
Cool-lights are often preferred to hot-lights by studio photographers. Since they don't become thermally hot, cool-lights don't create a risk of fire and they are more comfortable for a subject. Cool-lights often comprise fluorescent lights and emit light with a color temperature of about 5,500K. As such, cool-lights are often useful if there is ambient daylight, which has a color temperature of about 5,500K, in the studio and they can be used in conjunction with flash. However, as with hot-lights, cool-lights often do not generate sufficient light for photographing people, particularly as compared to flash lighting. Thus, studio photographers using cool-lights are relegated to using high ISO settings on their camera while capturing images, which again may detract from the quality of images being captured.
Due to recent advances in light-emitting diode (LED) technologies, LEDs lighting systems are an emerging lighting source that is well suited for studio lighting use. In an LED studio light, a multiplicity of LEDs, comprising an LED array, are configured in a variety of sizes and formats. These formats include flat panel light arrays, diffused light panels, spot lights, and flood lights. LEDs can be adjusted to emit light at different color temperatures. As continuous light source, LEDs are easy to use when lighting a subject, give off low levels of heat, and are power efficient.
In addition continuous lighting, “strobe” or “electronic flash” lighting is a highly popular choice that offers a great degree of control and flexibility. Electronic flashes are typically daylight balanced (5,500K) and can be used for studio applications. When lighting with electronic flash, the exposure is made by the discharge of a powerful micro-burst of light, which is generated by a power pack, or generator, and output through the flash's lamp head. Because the exposure is captured in a single, instantaneous, and powerful flash of light, flash lighting is ideal for stopping fast-moving subjects, living and otherwise. The power output of studio flash is measured in Watt-seconds (W/s). The least powerful electronic flash packs are rated as low as 100 W/s, while the largest flash packs are rated at 6400 W/s. Flash durations vary from about 1/100th second, to micro-bursts that are as short as 1/12,000 second, depending on whether the pack is set to full output power or a lower output setting. The ability to precisely adjust the intensity of the light as well as the option to sync with faster shutter speed of the photographer's camera make electronic flash lighting systems suitable for capturing subjects in motion.
However, even new and sophisticated light sources still pose challenges for photography. An issue with known LED lighting is that the intensity of the light emitted by the LED array is prone to varying, sometimes rapidly, over time. Similarly, the spectral distribution of the light source, the color of light emitted by the light source, can sometimes vary rapidly over time. Solutions to the problems these issues pose and methods for how to alleviate them, require complex measurement and analysis of variations in lighting. This complex measurement and analysis is typically performed in-camera. As can be appreciated, a disadvantage to such a solution is the additional complexity, and thus increased cost, of a camera embodying the technology to perform the complex measurement and analysis. Another disadvantage is that there can be inaccuracies resulting from imperfect measurements or modeling of predictable variations in lighting parameters. Another disadvantage is that there can be inaccuracies resulting from unpredictable variations in lighting parameters.